Hitachi ZW180 Technical Manual page 126

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Lift Arm Raise/Right Steering
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When the steering wheel is turned to the right with
the lift arm raised, pilot pressure shifts the lift arm
spool in the control valve and the steering valve
spool.
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Pressure from the own pump is applied to port
LS1 of the priority valve through orifice 1. Main
pressure returning from the steering valve spool
through orifice 3 and the spring force are applied
to port LS2.
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Pressure at port LS2 changes in proportion to the
steering valve spool movement. When pressure
at port LS2 is low, the priority valve spool moves
leftward slightly, and when it is high, the spool
moves leftward drastically.
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Flow rate and direction of the main pump are
controlled by the leftward movement of the priority
valve spool. The oil flow rate corresponding to the
movement flows to the steering valve, and the
remainder flow rate flows to the control valve.
NOTE: If the steering wheel is turned quickly and
largely for reasons of avoiding danger or
something, the priority valve spool largely
moves leftward, and much of pressure oil
from the main pump is supplied to the
steering
attachment moves slowly.
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Pressure oil to the steering valve flows to the
steering cylinders and the machine turns to the
right.
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Pressure oil to the control valve also flows to the
lift arm cylinder though the check valve and the lift
arm spool, and raises the lift arm.
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In this way, steering and lift arm operations are
simultaneously made.
SYSTEM / Hydraulic System
valve. Therefore the front
T2-3-10